Question about sims relationships?

So, I've noticed sims will disappear from my sims relationships. And then when I make them meet again I get the option to introduce them like they've never even met! For example my sim and a random sim I had made were my first two sims (his name is Bobby) and they were friends. Since then my sim has obviously talked to a lot of other sims, and now Bobby is nowhere on my sims relationships tab. Just random sims and pets shes spoken to like, once. Is there a way to fix this? Or is it even broken at all I'm not sure lol